Not worth using. Could be better.

At Newark airport: Firstly, in immigration, you have to wait on the "foreign officials" line. It takes longer for these individuals to go through so you lose some time. Secondly, there is no separate line in customs for those using this app, so any time gained in immigration, is lost in customs. Finally, there are signs everywhere "NO CELLPHONES". So you have to be willing to endure being yelled at multiple times, by multiple agents.

For the aforementioned reasons I do not recommend this app. If they have a separate lane, after getting suitcases, in customs (like a "priority" lane or "pre-check" lane by security) then it might be worth using.

saimaipaigai about Mobile Passport by Airside, v1.1.3